Contribution of Serum Leptin to Metabolic Syndrome in Obese and Nonobese Subjects

Background and Aims: Little evidence exists regarding the association of leptin with metabolic syndrome (MetS) as defined by conventional criteria. Moreover, the contribution of obesity to this relationship is not well understood. This study aimed to evaluate the association between leptin concentrations with MetS in obese and nonobese subjects. Methods: Data from the Third National Surveillance of Risk Factors of Non-Communicable Diseases (SuRFNCD) in Iran was used. In a cross-sectional study of 3045 adults (48.2% men) aged 25-64 years, anthropometric indices, blood pressure, fasting plasma glucose, fasting insulin, lipid profile [triglycerides, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and triglycerides], and fasting leptin were measured. Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) was also calculated. Results: Leptin concentrations were 2.6 fold higher in women compared with men. Subjects with MetS had significantly higher leptin concentrations. Leptin concentrations increased steadily with an increment in the number of MetS components (p <0.001). Leptin was significantly associated with MetS after adjustment for age, cigarette smoking, medication use, physical activity, HOMA-IR, and LDL-C. The significant association between leptin and MetS persisted after adjustment for body mass index (OR: 1.31, 95% CI: 1.09-1.58 in males and 1.17, 95% CI: 1.01-1.38 in females) and waist circumference (OR: 1.24 95% CI: 1.01-1.51 in men and 1.22, 95% CI: 1.04-1.43 in women). After dividing subjects into obese and nonobese, leptin concentrations were again significantly higher in subjects with MetS in both groups. Conclusions: We demonstrated that leptin concentrations are significantly associated with International Diabetes Federation (IDF)-defined MetS, independent of overall and central obesity. Our findings point to an independent role for leptin in development of MetS.